Re: [v6ops] AWS ipv6-only features

[Philip Homburg <[e-mail]>]

> > Is this common practice somewhere? Do people expect that something sensible
> > will happen if you try that? Is it documented what should happen?
> 
> Probably more common in mDNS than DNS, but yes, something sensible
> SHOULD happen as documented in the RFCs:
> 
> AAAA record sorting in getaddrinfo() or getnameinfo() should return
> the ULA records before the GUA records in the linked list.
> 
> As a result, an application that sensibly iterates through the list
> in order (as is expected behavior) should connect via GUA if possible
> (if not, it should rapidly receive an error and move on to the next
> item in the list, so no extraordinary processing or coding is
> required in the application).

mDNS is a bit of a boring case. If you get an mDNS reply is likely that the
destination is on the same subnet. It is possible to mess that up, but
that is more upto the network admin.

With DNS, how is it sensible to put both a ULA and a GUA in a single
DNS record?  Without happy eyeballs (and anything that is not
a webbrowser is unlikely to implement happy eyeballs), putting in two 
addresses for a host just means waiting twice as long when the host is
down.

What benefit do you expect to get from putting two addresses for the same
host in DNS (at the same DNS name, in the same view)?

Having two views (or names), one for external use with a GUA and one internal
use with ULA makes sense.